Introduction Unicompartmental knee arthroplasty (UKA) is well established in the treatment of OA of the knee, but has not been performed in large numbers compared with total knee arthroplasty. However, with the development of minimally invasive surgery, numbers of procedures are increasing rapidly. This study examines the results of minimally invasive UKA performed by one surgeon since august 1998.

Methods A consecutive series of 388 knees in 360 patients operated between August 1988 and February 2003 were evaluated using a prospective database. All surgeries were performed by the senior author using a minimally invasive technique in a day surgery unit. General anaesthesia was used in all cases with local anaesthesia intra-operatively, combined with an anaesthetic infusion pump. No patient received parenteral narcotics. Ninety-seven percent were medial and three percent were lateral arthroplasties.

Results Post-operatively no patients were lost to follow-up which ranged from two months to 4.5 years. Average age was 66 years. The average IKS score improved from 75 to 158 post-operatively. Most patients retained their pre-operative range of motion which averaged 120°. Average length of stay was 1.57 days with 41% of patients discharged the same day. There were five failures, due in part to osteoporosis and overcorretion. These were revised successfully to a ‘primary’ type knee prosthesis. Satisfaction rate subjectively was 98%.

Conclusions Mid term results of UKA using the Repicci technique of minimally invasive surgery with rapid mobilisation and early discharge has ahcieved excellent results for unicompartmental OA of the knee. The procedure is better tolerated with a low complication rate and higher patient satisfaction than total knee replacement in this gourp of patients.